The Experts below are selected from a list of 110052 Experts worldwide ranked by ideXlab platform
Ali H. Nayfeh - One of the best experts on this subject based on the ideXlab platform.
-
adaptive control of Flexible Structures using a nonlinear vibration absorber
Nonlinear Dynamics, 2002Co-Authors: O N Ashour, Ali H. NayfehAbstract:A nonlinear adaptive vibration absorber to control the vibrations ofFlexible Structures is investigated. The absorber is based on thesaturation phenomenon associated with dynamical systems possessingquadratic nonlinearities and a two-to-one internal resonance. Thetechnique is implemented by coupling a second-order controller with thestructure through a sensor and an actuator. Energy is exchanged betweenthe structure and the controller and, near resonance, the structure'sresponse saturates to a small value.
-
a nonlinear vibration absorber for Flexible Structures
Nonlinear Dynamics, 1998Co-Authors: Shafic S. Oueini, Ali H. Nayfeh, Jon R PrattAbstract:An approach for implementing an active nonlinear vibration absorber for Flexible Structures is presented. The technique exploits the saturation phenomenon exhibited by multidegree-of-freedom systems with quadratic nonlinearities possessing two-to-one autoparametric resonances. The strategy consists of introducing second-order controllers and coupling each of them with the plant through a sensor and an actuator, where both the feedback and control signals are quadratic. Once the structure is forced near its resonances, the oscillatory response is suppressed through the saturation phenomenon. We present theoretical and experimental results of the application of the proposed vibration absorber. The structure consists of a cantilever beam, the feedback signal is generated by a strain gage, and the actuation is achieved through piezoceramic patches. The equations of motion are developed and analyzed through perturbation techniques and numerical simulation. Then, the strategy is tested by assembling the controllers in electronic components and suppressing the vibrations of the first and second modes of two beams.
Anthony Tzes - One of the best experts on this subject based on the ideXlab platform.
-
closed loop input shaping for Flexible Structures using time delay control
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2000Co-Authors: Vikram Kapila, Anthony TzesAbstract:Input shaping techniques reduce the residual vibration in Flexible Structures by convolving the command input with a sequence of impulses. The exact cancellation of the residual structural vibration via input shaping is dependent on the amplitudes and instances of impulse application. A majority of the current input shaping schemes are inherently open-loop where impulse application at inaccurate instances can lead to system performance degradation. In this paper, we develop a closed-loop control design framework for input shaped systems. This framework is based on the realization that the dynamics of input shaped systems give rise to time delays in the input. Thus, we exploit the feedback control theory of time delay systems for the closed-loop control of input shaped Flexible Structures. A Riccati equation-based and a linear matrix inequality-based frameworks are developed for the stabilization of systems with uncertain, multiple input delays. Next, the aforementioned framework is applied to two input shaped Flexible structure systems. This framework guarantees closed-loop system stability and performance when the impulse train is applied at inaccurate instances. Two illustrative numerical examples demonstrate the efficacy of the proposed closed-loop input shaping controller.
-
closed loop input shaping for Flexible Structures using time delay control
Conference on Decision and Control, 1999Co-Authors: Vikram Kapila, Anthony TzesAbstract:We develop a closed-loop control design framework for input shaped systems. This framework is based on the realization that the dynamics of input shaped systems give rise to time delays in the input. Thus, we exploit the feedback control theory of time delay systems for the closed-loop control of input shaped Flexible Structures. A Riccati equation-based and a linear matrix inequality-based frameworks are developed for the stabilization of systems with uncertain, multiple input delays. Next, the aforementioned framework is applied to an input shaped Flexible structure system. This framework guarantees closed-loop system stability and performance when the impulse train is applied at inaccurate instances. A simulation study demonstrates that the closed-loop system with the proposed time delay controller outperforms the open-loop, input shaped system and the standard linear quadratic regulator when the impulse is applied at an inexact instance.
-
An Adaptive Input Shaping Control Scheme for Vibration Suppression in Slewing Flexible Structures
IEEE Transactions on Control Systems Technology, 1993Co-Authors: Anthony Tzes, Steve YurkovichAbstract:The application of an input precompensation scheme for vibration\nsuppression in slewing Flexible Structures, with particular application\nto Flexible-link robotic manipulator systems, is considered. The control\nfrom such input shaping schemes corresponds to a feedforward term that\nconvolves in real time the desired reference input with a sequence of\nimpulses and produces a vibration-free output. The robustness of such an\nalgorithm with respect to modal frequency variations is not satisfactory\nbut can be improved by convolving the input with a longer sequence of\nimpulses, the tradeoff being a decrease in the transient response speed.\nAn adaptive precompensation scheme that can be implemented by combining\na frequency domain identification scheme, used to estimate the modal\nfrequencies online, with a subsequent scheme for adjusting the spacing\nbetween the impulses is proposed. The combined adaptive input shaping\nscheme provides the most rapid slew that results in a vibration-free\noutput. Experimental results for a single Flexible link are presented to\nverify the technique
V Feliu - One of the best experts on this subject based on the ideXlab platform.
-
a fast online estimator of the two main vibration modes of Flexible Structures from biased and noisy measurements
IEEE-ASME Transactions on Mechatronics, 2015Co-Authors: Andres Sanmillan, V FeliuAbstract:Vibrations are present in many mechanical Structures and machines, and are often associated with their elastic parts. Characterizing these vibrations, i.e., obtaining their frequencies, amplitudes and phases, is of most interest in many applications ranging from the maintenance of civil Structures to motion control. This paper presents a method for the online and reliable identification of the defining parameters of two unknown sinusoidal signals through the use of their measured sum in the presence of noise and an offset. It is based on the algebraic derivative approach, defined in the frequency domain, which yields exact calculation formulae for the unknown parameters of the signal, i.e., the amplitudes, phases, and frequencies of the two sinusoids and the value of the constant term. The online estimation is performed in a time interval which is only a fraction of the first full cycle of the slower component of the measured signal. This feature allows the algorithm to be used to monitor time-varying parameters in these vibration signals. This algorithm has been used in experiments with a Flexible beam, which is a representative platform of a vibrating mechatronic system. It estimated all the vibration signal parameters quickly and accurately, proved to be insensitive to high-frequency noises, and accurately tracked the time variations of the signal parameters.
-
brief paper adaptive input shaping for manoeuvring Flexible Structures using an algebraic identification technique
Automatica, 2009Co-Authors: Emiliano Pereira, Juan R Trapero, Ivan M Diaz, V FeliuAbstract:Input shaping is an efficient feedforward control technique which has motivated a great number of contributions in recent years. Such a technique generates command signals with which manoeuvre Flexible Structures without exciting their vibration modes. This paper presents a novel adaptive input shaper based on an algebraic non-asymptotic identification. The main characteristic of the algebraic identification in comparison with other identification methods is the short time needed to obtain the system parameters without defining initial conditions. Thus, the proposed adaptive control can update the input shaper during each manoeuvre when large uncertainties are present. Simulations illustrate the performance of the proposed method.
Jon R Pratt - One of the best experts on this subject based on the ideXlab platform.
-
a nonlinear vibration absorber for Flexible Structures
Nonlinear Dynamics, 1998Co-Authors: Shafic S. Oueini, Ali H. Nayfeh, Jon R PrattAbstract:An approach for implementing an active nonlinear vibration absorber for Flexible Structures is presented. The technique exploits the saturation phenomenon exhibited by multidegree-of-freedom systems with quadratic nonlinearities possessing two-to-one autoparametric resonances. The strategy consists of introducing second-order controllers and coupling each of them with the plant through a sensor and an actuator, where both the feedback and control signals are quadratic. Once the structure is forced near its resonances, the oscillatory response is suppressed through the saturation phenomenon. We present theoretical and experimental results of the application of the proposed vibration absorber. The structure consists of a cantilever beam, the feedback signal is generated by a strain gage, and the actuation is achieved through piezoceramic patches. The equations of motion are developed and analyzed through perturbation techniques and numerical simulation. Then, the strategy is tested by assembling the controllers in electronic components and suppressing the vibrations of the first and second modes of two beams.
Steve Yurkovich - One of the best experts on this subject based on the ideXlab platform.
-
An Adaptive Input Shaping Control Scheme for Vibration Suppression in Slewing Flexible Structures
IEEE Transactions on Control Systems Technology, 1993Co-Authors: Anthony Tzes, Steve YurkovichAbstract:The application of an input precompensation scheme for vibration\nsuppression in slewing Flexible Structures, with particular application\nto Flexible-link robotic manipulator systems, is considered. The control\nfrom such input shaping schemes corresponds to a feedforward term that\nconvolves in real time the desired reference input with a sequence of\nimpulses and produces a vibration-free output. The robustness of such an\nalgorithm with respect to modal frequency variations is not satisfactory\nbut can be improved by convolving the input with a longer sequence of\nimpulses, the tradeoff being a decrease in the transient response speed.\nAn adaptive precompensation scheme that can be implemented by combining\na frequency domain identification scheme, used to estimate the modal\nfrequencies online, with a subsequent scheme for adjusting the spacing\nbetween the impulses is proposed. The combined adaptive input shaping\nscheme provides the most rapid slew that results in a vibration-free\noutput. Experimental results for a single Flexible link are presented to\nverify the technique
